Descriptions

This study conducted well-to-pump and well-to wheel life-cycle assessment of fossil
energy use and greenhouse gas (GHG) emissions during ethanol production from
tropical Banagrass (Pennisetum purpureum) using green-processing (with the use of
fresh feedstocks) and dry or conventional processing (with the use of dried
feedstocks) in the state of Hawaii. 10 000 MJ of energy was used as a functional unit
with a systematic boundary drawn based on relative mass, energy, and economic
value method using a 1% cutoff value, and the results were compared to those of
conventional gasoline, and ethanol from corn and other ethanol lignocellulosic
feedstocks. Detailed techno-economic model was built using the SuperPro designer.
Ethanol yields were estimated at 0.27 l/kg (green processing with fungal co-product),
0.27 l/kg (green processing without co-product), and 0.29 l/kg (dry-processing) of
feedstock, respectively. The well-to-pump analysis indicate that ethanol production
consume 8200 MJ (green processing with co-product), 7600 MJ (green-processing
without co-product) and 7200 MJ (dry-processing without co-product) of fossil
energy and emit approximately 144 kg CO₂-eq., 90.6 kg CO₂-eq., and 59.1 kg
CO₂-eq. per 10 000 MJ of ethanol produced, respectively; well-to-wheel analysis
showed that 280 g of gCO₂-eq., 260 g CO₂-eq., and 250 g CO₂-eq. of emissions were
produced per kilometer by driving Flex Fuel Vehicle. In summary, ethanol produced
using the green-processing technology required greater amount of fossil energy and
produced more GHG emissions compared to that of dry processing technology, due
to additional energy needed for fungal growth and related processes. Process power,
enzyme, and chemical production during ethanol processing were identified as
emissions hot-spots for both green and dry processing.